fs/libfs.c: add generic data flush to fsync

Description by Jan Kara:
"A lot of older filesystems don't properly flush volatile disk caches
on fsync(2) which can lead to loss of fsynced data after power failure.

This patch makes generic_file_fsync() issue proper cache flush to fix the
problem.  Sysadmin can use /sys/devices/.../cache_type to tell the system
it should not send the cache flush."

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Suggested-by: Jan Kara <jack@suse.cz>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/libfs.c b/fs/libfs.c
index a1844244246f8e8e8da60da61e2aaabd2750e58e..3a704e194d635efe8a29ed1c62efe2b6c4afc707 100644 (file)
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -3,6 +3,7 @@
  *     Library for filesystems writers.
  */
 
+#include <linux/blkdev.h>
 #include <linux/export.h>
 #include <linux/pagemap.h>
 #include <linux/slab.h>
@@ -923,16 +924,19 @@ struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid,
 EXPORT_SYMBOL_GPL(generic_fh_to_parent);
 
 /**
- * generic_file_fsync - generic fsync implementation for simple filesystems
+ * __generic_file_fsync - generic fsync implementation for simple filesystems
+ *
  * @file:      file to synchronize
+ * @start:     start offset in bytes
+ * @end:       end offset in bytes (inclusive)
  * @datasync:  only synchronize essential metadata if true
  *
  * This is a generic implementation of the fsync method for simple
  * filesystems which track all non-inode metadata in the buffers list
  * hanging off the address_space structure.
  */
-int generic_file_fsync(struct file *file, loff_t start, loff_t end,
-                      int datasync)
+int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
+                                int datasync)
 {
        struct inode *inode = file->f_mapping->host;
        int err;
@@ -952,9 +956,38 @@ int generic_file_fsync(struct file *file, loff_t start, loff_t end,
        err = sync_inode_metadata(inode, 1);
        if (ret == 0)
                ret = err;
+
 out:
        mutex_unlock(&inode->i_mutex);
        return ret;
+}
+EXPORT_SYMBOL(__generic_file_fsync);
+
+/**
+ * generic_file_fsync - generic fsync implementation for simple filesystems
+ *                     with flush
+ * @file:      file to synchronize
+ * @start:     start offset in bytes
+ * @end:       end offset in bytes (inclusive)
+ * @datasync:  only synchronize essential metadata if true
+ *
+ */
+
+int generic_file_fsync(struct file *file, loff_t start, loff_t end,
+                      int datasync)
+{
+       struct inode *inode = file->f_mapping->host;
+       int err;
+
+       err = __generic_file_fsync(file, start, end, datasync);
+       if (err)
+               return err;
+#ifdef CONFIG_BLOCK
+       return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
+#else
+       return err;
+#endif
+
 }
 EXPORT_SYMBOL(generic_file_fsync);
 

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 878031227c57a0b41be7cde3070ee90f1921b570..c3f46e499dd0027eed7f2bd0a0bc3cd465c3ac44 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2590,6 +2590,7 @@ extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
 extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
                const void __user *from, size_t count);
 
+extern int __generic_file_fsync(struct file *, loff_t, loff_t, int);
 extern int generic_file_fsync(struct file *, loff_t, loff_t, int);
 
 extern int generic_check_addressable(unsigned, u64);